Science

What NASA’s successful DART mission means for the future of planetary defense

Etiamophobia is the fear of an asteroid hitting the Earth, presumably ending all life as we know it. While improbable before, we now have a means to protect humanity from the whims of an unpredictable universe. 

On Monday evening, about seven million miles away, NASA’s Double Asteroid Redirection Test (DART), at last made contact with the asteroid Didymos and its football stadium-sized moonlet, a particularly small natural satellite, Dimorphus. The spacecraft journeyed for a little over 10 months to test if it would be possible to save Earth from future hazardous asteroids or comets by booting them off course. 

“We only have one home so we ought to take care of it,” said NASA Administrator Bill Nelson during a DART mission overview briefing on Monday afternoon before the mission collision. He went on to note that DART is “the world’s first mission to test the technology for defending Earth against an incoming killer asteroid.” 

Thanks DART. You’ve served your purpose. This is the last complete image of asteroid moonlet Dimorphos before DART smashed into the surface. NASA/Johns Hopkins APL

While Earth is bombarded by asteroids and smaller meteors on a fairly regular basis, not many are noticed or pose any danger to life on the planet. While humans (so far) have been luckier than the dinosaurs, there’s no telling if Earth’s good fortune will hold up. In fact, the largest recorded asteroid impact to date happened only 115 years ago, when an asteroid the size of a 25 story-building flattened about 800 square miles of forest in an uninhabited area of Siberia, Russia. Lindley Johnson, NASA’s planetary defense officer, told Popular Science that if a similar impact were ever to occur in a metropolitan area, it would most certainly be on the scale of a natural disaster. Johnson says that DART is a “significant milestone” in humanity’s capabilities to protect the planet from such a dark outcome.

“This is the first time that humankind acquired the knowledge and the technology to start to rearrange things a little bit in the solar system, if you will, and make it a more hospitable place for life,” Johnson says.

[Related: NASA’s first attempt to smack an asteroid was picture perfect]

In the minutes before impact, DART hurled toward the moonlet at more than 14,000 miles per hour, before striking 17 meters from the craggy center and utterly destroying itself around 7:14pm EDT. By crashing the more than $3 million probe into the Didymos’ satellite, scientists expect the hit to have shaved at least a fraction of a millimeter per second off Dimorphus’ orbital speed. As DART is about 11 billion pounds smaller than its target, the craft aimed to alter the asteroid’s course, which takes less energy than trying to completely obliterate it, says Johnson. Ultimately, pushing the asteroid away is a safer and altogether surer protective maneuver. “You can never really be assured that you’re going to completely break up an asteroid or destroy it,” he says. “If you’ve done nothing to change its orbit, then you’ve just got a bunch of pieces that are headed at you.” It also saves what could be a precious amount of time before planet impact and maintains more control over the object. 

While the data from the collision is still being collected and processed, humanity’s first attempt at moving a celestial object and its first planetary defense test seems to have been a success: Along with the loss of camera visuals, the spacecraft’s impact was confirmed by a loss of signal. Although it could take anywhere from weeks to a few months before NASA knows just how far the mission was able to push the asteroid out of orbit, the spacecraft’s ability to nail its target has catapulted the concept of planetary defense out of the realm of doomsday-esque movie plots and into a real-life solution. Yet what does this triumphant first step mean for the advancement of other precautionary measures?

While the DART spacecraft met its valiant end, NASA scientists say that the real science of the mission has only just begun. Telescopes on Earth have spent years studying and measuring the Didymos-Dimorphus system, and those same telescopes will now be trained on the system to make new measurements on its orbit relative to what it was before. Other missions that survey the vast sky, like the James Webb Space Telescope, will also soon point towards the asteroid system, said Elena Adams, DART missions systems engineer at Johns Hopkins Applied Physics Laboratory, during a post-impact panel on Monday night. NASA and the public could also get images of the system from other active crafts like LICIACube, LUCY, as well as the Hubble Space Telescope

[Related: When Voyager 1 goes dark, what comes next?]

And the US isn’t the only nation investing in our planet’s defenses. In October 2024, the European Space Agency will send another probe, HERA, to examine the aftermath of the DART mission, making a detailed impact survey that will give scientists information they need to understand the experiment well enough to do again, with even more success. DART is only the beginning, but it marks the dawn of a universe where humans aren’t just passive residents, but where we can be assured of our place among the inconstant cosmos.  



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